The present invention relates to an industrial vehicle such as a forklift truck.
The forklift truck is widely used as the industrial vehicle to perform loading operation (operation for picking up or putting down load) in a factory yard. In such a forklift truck, an operator or driver of the forklift truck is engaged in not only driving the vehicle but also loading. The driver therefore frequently leaves the seat of the vehicle in an idling state, which may cause a dangerous state. To avoid it, Japanese Unexamined Utility Model Publication No. 2-51934 proposes a safety device for use in restoring a running state of the vehicle after the driver leaves the seat.
In the above reference, the seat is provided with a seat switch for detecting whether the driver is seated. If the seat switch detects that the driver is not seated, energization of a solenoid valve is broken. The solenoid valve changes flow of hydraulic fluid into a transmission (clutch mechanism) connected to an engine. If the driver who has left the seat returns to the vehicle, when the driver is seated and a manipulation position of a lever for forward or backward movement is a neutral position, the solenoid valve is reenergized.
Meanwhile, there is a way that a detection switch directly detects whether the manipulation position of the lever is a position of the forward movement or a position of the backward movement and judges that the neutral position is detected if the manipulation position is neither the position of the forward movement nor the position of the backward movement. In the forklift truck using such a detection way of the manipulation position, if the solenoid valve is reenergized under the condition of the return of the safety device as described in the above reference, the forklift truck has the following problems.
That is, in the case of the above detection way, if the connection between the detection switch and a controller is broken, the controller erroneously judges that the manipulation position of the lever is the neutral position. Therefore, if the driver leaves the seat with the lever manipulated in the position of the forward or backward movement and the connection between the detection switch and the controller is then broken in this state, when the driver is seated, it is erroneously judged or detected that the manipulation position of the lever is the neutral position, thereby to restore the running state. Consequently, the running state is restored only by the judgment of the seat switch that the driver is seated. Therefore, when the safety device of the above reference is applied to the forklift truck which uses the above detection way, the safety device is subject to an influence (such as disconnection) of various detection switches for detecting condition that restores the running state, so that reliability of the safety device deteriorates. If the running state of the vehicle, especially with the torque converter is restored under the above condition, the vehicle may run away due to a creep phenomenon of the toque converter by reenergizing the solenoid valve.
The present invention is directed to an industrial vehicle which prevents erroneous return of the running state due to erroneous detection of various detection switches by adding driving manipulation of the driver to the condition of the return of the running state when the running state is restored after the driver leaves the seat, thereby to improve reliability of the return of the running state.